1. Field of the Invention
The present invention relates to solid siliconized polyester resins, coating compositions containing the resin, coatings made from the coating composition, products coated by the coatings, and methods for making the same.
2. Background Art
Polyester resins have been used in industry for years as a binder for making conventional baking enamels and thermoset powder coatings for industrial, architectural, and maintenance coatings. Polyester resins with hydroxy functional groups lend themselves to being used in combination with crosslinkers such as melamine or isocyanates.
The incorporation of silicone into the backbone of the polyester polymer increases the heat resistance and UV resistance of the polymer, which moves the conventional polyester from low durability to high durability. Incorporating silicone into the backbone of the polyester increases the heat resistance of the resulting polymer makes it more suitable for use in coatings for mufflers, cookware and bakeware products, automotive products, architectural products. Coatings currently utilizing this approach are liquid silicone modified polyester and are generally in solution containing between 50–70% solids.
The current trend is to move to low VOC coatings, and therefore a solid version of silicone modified polyester (SMP) would be ideal for powder coatings applications. The conventional technology utilizes liquid or flake silicone intermediates, which have low glass transition temperatures (Tg) and will not form stable SMP flakes. The use of the low Tg intermediate forms a SMP, which will re-agglomerate over time forming large lumps, which renders the resulting SMP unsuitable for use in power coatings.
Accordingly, it will be desirable to provide a suitable solid silicone modified polyester and coating that overcomes at least one problem in the prior art.